This invention relates generally to gas generation and, more particularly, to methods for producing or forming gas producing reactions mixtures in or for airbag inflator devices as well as the inflator devices so produced.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion,” that is inflated or expanded with gas such as when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated, in a matter of no more than a few milliseconds, with gas produced or supplied by a device commonly referred to as an “inflator.”
Many types of inflator devices have been disclosed in the art for the inflating of one or more inflatable restraint system airbag cushions. Known types of inflator devices include inflators known as “blow down” inflators and “reverse flow” inflators. In a blow down inflation system, a pyrotechnic or other selected material is commonly burned to create a build-up of pressure within a compressed gas storage chamber such as to result in the rupture or release of inflation gas therefrom when the internal pressure reaches a predetermined level or range. Thus, in blow down inflator devices, the opening or rupture of a seal, burst disk or the like within the inflator typically results or produces a flow of heated or elevated temperature inflation gas from the device and into an associated airbag cushion. While blow down inflation systems can desirably be of relatively lower cost and complexity, such systems can result in the delivery of inflation gas to an associated airbag cushion at a higher temperature, pressure and/or mass flow rate than may otherwise be desired.
In “reverse flow” inflator devices, the actuating initiator and the openings wherethrough the inflation gas exits from the inflator device are typically at or along the same end or side of the inflator device. Thus, in typical reverse flow inflators, the initial inflation gas exiting from the inflator device and into an associated airbag cushion is relatively cool and is later followed by heated or elevated temperature inflation gas. Consequently, reverse flow inflators which initially provide or supply a relatively cool inflation gas, followed by heated or elevated temperature inflation gas to an associated airbag cushion, can typically more easily provide or result in the more gradual deployment of the associated airbag cushion, as may be desired in particular deployment applications.
Various of such prior art inflator devices rely on the reaction of a fuel with an oxidant to produce or form a gaseous inflation medium. In addition, as disclosed in commonly assigned, Rink, U.S. Pat. No. 5,669,629, issued Sep. 23, 1997, whose disclosure is hereby incorporated by reference, it has been proposed various dissociation or decomposition sensitizer materials can be added or included with a dissociative or decomposable gas source material, such as nitrous oxide, such as to promote or accelerate the rate of the dissociation or decomposition reaction of the gas source material. As disclosed, such sensitizer materials are preferably added or included in an amount below the flammability limits for the content mix, such that the contents are preferably at an equivalence ratio of less than 0.25, preferably less than 0.15. At such low relative amounts, the contents are essentially non-flammable and thus combustion and the formation of combustion products are practically avoided.
While the separate storage or containment of fluid oxidant materials from such fuel or hydrocarbon or hydrocarbon derivative sensitizer may reduce or minimize at least some of the risks or dangers associated with the use of such material combinations, such separate storage or containment can undesirably increase the costs and complexity associated with manufacture and production as well as increase the complexity of operation such as may impair performance reliability. Further, inflator devices which rely on the reaction of a fuel with a fluid oxidant generally exhibit improved performance, as evidenced by increased efficiency, when such fuel and fluid oxidant are in a well mixed form. In view thereof, the use of co-existing mixtures of various hydrocarbon fuels and a selected oxidant has been proposed. Unfortunately, the manufacture of inflators using such premixed fuel and fluid oxidant mixtures can be problematic. For example, welding, such as may be desired in various inflator designs, can be dangerous when done in the presence of a volatile mixture of fuel and oxidant.
One approach that has been applied in an effort to reduce or minimize the risks or dangers associated with the use of premixed fuel and fluid oxidant mixtures has been to rely on mixtures of fuel and oxidant, which mixtures are very fuel lean. While fuel lean mixtures may reduce some of the risks or hazzards associated with using fuel-oxidant mixtures, such use typically does not eliminate the risks associated with such mixtures and may create or compound other problems or complications. For example, the use of very fuel lean mixtures can lead to performance and ignition problems or complications.
Thus, while premixed combinations of fuel, particularly hydrocarbon fuels, and oxidants can generally greatly enhance performance, such oxidant and fuel mixtures or combinations have been difficult to either or both prepare and manufacture. In view thereof, there is a need and a demand for methods which more easily permit the formation and use of mixtures of fuel and oxidant in a device as well as improved inflator devices having or which contain such fuel and oxidant mixtures.